An angular limb deformity is a contortion of the limb resulting from improper alignment of bone growth.

Damage to the zone of bone growth causes bending and twisting of the bones, resulting in the deformity.

Without correction, the deformity places abnormal stresses on joints, resulting in pain and arthritis.

Correction involves orthopedic surgery which reduces the chances of pain and arthritis in the long term.

What is it?

• Angular limb deformities (ALDs) are crooked or abnormally shaped limbs that occur when the bones of a limb do not grow in appropriate alignment.
• Most often occurs on the forelimb (radius/ulna) and hindlimb (tibia/fibula).
• Most often the result of an injury to the zone of bone growth (growth plate, or physis) in a young animal.
  
• The crooked bones place abnormal forces on joints, leading to pain and arthritis in the long term.
  
• Corrective surgery aims to restore the proper angle to the bone, reducing the longterm chances of arthritis.

Pertinent Anatomy

• The long bones grow by elongation at growth plates located at either end of the shaft.
  
• Damage to the cells in these growth plates causes premature cessation of growth.
  
• The entire growth plate may stop growing, resulting in shortening of the bone. This becomes complicated when two bones grow side-by-side, e.g. radius and ulna, and one of them stops growing, resulting in a bowing of the still-growing unaffected bone.
  
• A portion of the growth plate may stop growing, resulting in bending of the bone at that location.

Clinical Signs

• The pet may have suffered an injury while young (less than eight months old), e.g. getting stepped on, dropped, hit by a car, caught in a doorway, or getting tripped over.
  
• The owner will note the affected limb start to develop an angle, rather than grow straight as the pet ages; the photo above and right show the bend in the limb - dashed lines).
• Lameness may develop and the pet may no longer be walking flat on the paw.
• The owner may also note inability to sit or lie down properly, instead the leg may stick out at an angle.

Diagnosis

• The veterinarian will perform a full physical and orthopedic examination, looking at the range of motion of all joints, and comparing the affected and unaffected legs.
• For example, early closure of the distal ulnar growth plate causes shortening, cranial bowing, external rotation, and outward angulation of the radius.
• Damage to the growth plate of the radius results in shortening of the radius and subluxation (partial dislocation) of part (radiohumeral joint) of the elbow joint.
• If part, but not all, of a growth plate is damaged, then the affected bone will develop an angle at that plate (photo right).
• Radiographs to compare affected and unaffected legs will likely be taken.
  
• Labwork on blood and urine may be run to assess your pet’s current state of health in preparation for anesthesia.

Treatment

• The veterinary surgeon may require repeat radiographs taken under anesthesia for proper positioning.
  These radiographs are used to calculate angles and distances required for correction.
• There are several methods by which the surgeon makes the desired correction, depending on the amount of deformity and the age of the pet when presented.
• Corrective osteotomy is a planned cutting of the bone in order to restore correct alignment.
• Correction may involve removing a wedge of bone, making a semicircular cut and rotating the bone, and distraction or repositioning of the bones in the correct alignment.
• Once the bone pieces are realigned properly, rigid fixation is applied to hold the pieces together until bony healing has occurred. Fixation may involve plates, pins, screws, or external frames, and depends on the type of correction required (see photo above right).
• The photo to the right was taken 3 weeks after surgery. Take note of the straight alignment of the limb.
• Bony healing takes approximately two months of strict rest to protect the surgical implant from breaking, bending, or working its way out of the bone.
• Until bony healing has been confirmed by radiograph, the fixation device is the only thing holding your pet’s bone together.
• Recheck examination two weeks post-surgery ensures the surgical incision is healing appropriately.
• A recheck radiograph (to confirm bony healing) is usually taken 8 weeks after surgery.
• Antibiotics may be given if there is concern about infection.
• Pain control in hospital is provided by a combination of intravenous or intramuscular injections, oral medication, epidural or other nerve block, or transcutaneous patch.

Complications

• Too much activity post-operatively can cause the repair to fail, resulting in the need for a second surgery to fix the repair. This is why recommendations are made for strict rest during the two month healing period.
• As with all surgeries, there is risk associated with anesthesia – this is mitigated by pre-operative labwork, careful monitoring of blood pressure, ECG, temperature, depth, heart rate, heart rhythm, breathing rate, and blood loss. Responses are tailored to the needs of the pet.
• Post-operative infection is a possibility, particularly if the pet licks or chews at the incision. Antibiotics are the appropriate response.
• Rarely, a pet may have a reaction to the antibiotics prescribed. This typically manifests as vomiting or diarrhea, or, extremely rarely, as anemia. Please consult a veterinarian immediately if your pet is vomiting, has diarrhea, or is lethargic, depressed, and weak while on antibiotics.
• The pain medications (opioids) used immediately post-operatively may occasionally cause panting, disorientation, or weakness. Please consult a veterinarian if you are concerned that your pet is affected this way.
• The use of epidural morphine may cause urinary incontinence (dribbling). This typically resolves 8 to 12 hours after the last injection.
• Depending on your pet’s angular limb deformity, growth post-operatively, and bony healing post-operatively, multiple surgeries are sometimes required to achieve correction of the original deformity.

Home Care

• Two months of strict rest is prescribed: no running, jumping, rough-housing, or stairs, with short leash walks outside for bathroom duty only.
• The pet must not be allowed to lick at or chew the surgical site – this may cause infection or dehiscence (coming apart of the incision).
• The wound should be kept clean and dry, with daily inspections for increased discharge, reddening or swelling.
• Hot and cold packing will be recommended to help deal with post-operative swelling and aid in healing.
• Rehabilitation therapy will be recommended – this typically involves moving the affected joints through range of motion exercises for 5 to 10 minutes, several times a day.
• A sling may be provided for the client to offer additional support to the pet while the pet walks at first. This helps to catch the pet if the pet slips and falls, so as to prevent extra stress on the fixation device.
• Pain control at home is provided by a combination of epidural catheter injections (training is provided as to how to perform these), transcutaneous patch, or oral medications.

Prognosis

• Prognosis is good for restoration of function to a deformed limb with corrective surgery.
  Restoration of function will also delay the onset and reduce the severity of potential arthritis in associated joints.
  
• Without surgery, the patient is at risk of a lifetime of pain and arthritis as a result of the unnatural forces the deformity places on the associated joints.

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